Half-round jaws are primarily used to make "go-no-go" or snap gages to verify the diameter of a hole. The radius on the jaws is to allow the jaw to come into contact with the wall of the hole. This cannot be done with a straight jaw. Gage blocks and half-round jaws are assembled into a combination. The combination is inserted into a hole. Measurement is made by checking whether the combination fits into the hole, or it doesn’t.

See Data Sheet for additional details.